1. Field of the Invention
The present invention relates to a magnetic recording medium, such as a magnetic tape, in which servo signals are written, a servo signal write head unit for writing servo signals in the magnetic recording medium, and a servo writer including the servo signal write head unit.
2. Description of the Related Art
Conventionally, in order to allow a read/write element of a magnetic head to track data tracks of a magnetic tape in which magnetic information is to be recorded, servo signals are written in the magnetic tape. A timing base technique has been known as a technique for writing servo signals in a magnetic tape (For example, refer to U.S. Patent Application Publication No. 5,689,384). As shown in, for example, FIG. 9A, writing of servo signals in this technique is achieved by forming a first magnetizing area SP1 and a second magnetizing area SP2 in a servo band SB extending along the running direction of a magnetic tape MT so as to cross the servo band SB.
In this example, as shown in FIG. 9B, a servo pattern SP is composed of a combination of the first magnetizing area SP1 and the second magnetizing area SP2. Specifically, the first magnetizing area SP1 is inclined at a predetermined angle θ with respect to the width direction of the servo band SB, and the second magnetizing area SP2 is inclined at an angle differing from the angle of the first magnetizing area SP1. The first magnetizing area SP1 and the second magnetizing area SP2 are formed and magnetized so that, as shown in FIG. 9A, the magnetizing direction of the servo band SB is oriented in one direction by a servo write head (not illustrated), that is, in the example shown in FIG. 9A, oriented in the direction shown by the magnetizing direction M. In addition, servo patterns SP each composed of the first magnetizing area SP1 and the second magnetizing area SP2 are repeatedly formed in the direction along which the servo band SB extends.
On the other hand, as shown in FIG. 9A, a read/write element RWD of the magnetic head H is constructed to trace a predetermined data track DT formed in the data band of the running magnetic tape MT, when the servo signal read element SRD of the magnetic head H traces, for example, the centerline L1 of the servo band SB. Furthermore, the servo signal read element SRD senses magnetic fluxes from the first magnetizing area SP1 and the second magnetizing area SP2 whenever the servo signal read element SRD crosses the two areas. At this time, the servo signal read element SRD senses the fluxes at constant timing as long as the servo signal read element SRD traces the centerline L1 of the servo band SB as shown in FIG. 9B. On the other hand, when the servo signal read element SRD traces the line L2, that is, a line at the side where the interval between the first magnetizing area SP1 and the second magnetizing area SP2 is shortened due to the displacement of the servo signal read element SRD in the width direction of the servo band SB, the time period when the servo signal read element SRD senses the fluxes is decreased. On the other hand, when the servo signal read element SRD traces the line L3, that is, a line at the side where the interval between the areas is widened, the time period is increased. In other words, the magnetic head H is positioned such that the sensing timing becomes a predetermined value, whereby the read/write element RWD of the magnetic head H can trace a predetermined data track DT.
However, it has been known that, in such a magnetic tape MT, the angle θ of the first magnetizing area SP1 (refer to FIG. 9B) is typically set to 6 degrees or less due to the azimuth loss, and if the angle θ exceeds 6 degrees, the output and SN ratio of servo signals deteriorate.
On the other hand, in recent years, high-density recording of magnetic tapes has advanced, and in the data bands DB (refer to FIG. 9A) of a magnetic tape MT, several hundreds of data tracks DT have been formed in the width direction of the magnetic tape MT. As a result, the widths and intervals of the data tracks DT are remarkably narrowed, and simultaneously, the widths of the data bands DB are also narrowed. In the future, it is considered that a further high-density recording of magnetic tapes MT will advance, wherein higher accuracy is required for positioning of the magnetic head H (refer to FIG. 9A) in the width direction of magnetic tapes MT.
As the widths of the servo bands SB are narrowed, it is more necessary to heighten resolution of servo signals in the width direction of the servo bands SB. Therefore, in order to enhance the resolution of servo signals in the width direction of the servo bands SB, it is considered that the angle θ of the first magnetizing area SP1 is defined to be a larger value. However, it is impossible to accurately position the magnetic head H with respect to the magnetic tape MT due to the azimuth loss described above if the angle θ of the first magnetizing area SP1 is set to exceed 6 degrees.
It is therefore an object of the present invention to provide a magnetic recording medium which enables a magnetic head to be accurately positioned even if higher-density recording of magnetic recording media is reinforced, a servo signal write head unit for writing servo signals in the magnetic recording medium for the purpose of obtaining such a magnetic recording medium, and a servo writer provided with the servo signal write head unit.